1. Field of the Invention
The present invention relates to a motor suitable for surface mounting on a circuit board.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 11-234943 discloses an example of a technique in this field. A surface mount motor described in this publication includes a motor body and a metal holder frame fixed to the motor body. The motor body is a brush motor and has a substantially columnar drum portion (motor casing). The rear end of the substantially columnar drum portion is closed by an end bracket made of resin. Terminal pieces (terminals) that are mounted on a circuit board and brush terminal pieces that slide with respect to a commutator are fixed to the end bracket. The metal holder frame includes a holder body that is attached to the drum portion of the motor body. The holder body includes a rectangular bottom plate portion which contacts the circuit board and a pair of clamping spring pieces that are bent upward from the long sides of the bottom plate portion and that clamp the substantially columnar drum portion of the vibration motor body. A bulge portion having a trapezoidal shape in cross section is formed on the bottom plate portion of the holder frame at a position corresponding to the center of gravity of the motor body. The drum portion of the motor body is placed on a top surface of the bulge portion, so that the motor body can be stably placed on the holder frame. Cream solder used for mounting the motor is introduced into the bulge portion while the cream solder is in a molten state. Accordingly, the holder frame does not easily become detached from the circuit board.
The bulge portion provided on the bottom plate portion of the holder frame is formed in a trapezoidal shape in cross section by press working. Therefore, there is a risk that the motor body will be inclined depending on the levelness and flatness of the top surface of the bulge portion. The shape accuracy of the bulge portion largely depends on the accuracy of the die used in press working. As the size of the holder frame decreases, it becomes more difficult to use a die having sufficient accuracy. It is necessary that the mounting surface of the bottom plate portion of the holder frame be in the same plane as the mounting surfaces of the terminal pieces. When the mounting surface of the bottom plate portion of the holder frame and the mounting surfaces of the terminal pieces are at different heights, it is difficult to perform a fine adjustment of the heights of the mounting surfaces by deforming the top surface of the bulge portion having a trapezoidal shape in cross section. Thus, in the holder frame according to the related art, it is difficult to adjust the heights of the mounting surface of the bottom plate portion of the holder frame and the mounting surfaces of the terminal pieces.